(1) Field of the Invention
The present invention relates to a novel cyanoguanidine derivative which is a precursor for the synthesis of N-cyano-N'-methyl-N"-(2-(5-methyl-4-imidazolylmethylthio)ethyl)guanidine (Cimetidine; often referred to as "Cimetidine" hereinafter), which has an action of controlling secretion of gastric acid and is valuable as an agent for the remedy of a gastric ulcer, and a process for the preparation of this cyanoguanidine derivative.
(2) Description of the Prior Art
Imidazole derivatives such as 4-hydroxymethyl-5-methylimidazole disclosed in Japanese patent application laid-open specification No. 142271/81, 4-(2-aminoethylthio)-5-methylimidazol disclosed in Japanese patent application laid-open specification No. 42661/72 and ((4-methyl-5-imidazolyl)methylthioethyl)-S-methylisothiourea disclosed in Japanese patent application laid-open specification No. 7557/74 are mainly used as the precursor for the synthesis of Cimetidine, and Cimetidine can be derived from these imidazole derivatives. Separately, N-cyano-N'-2-2(2,3-diketobutylthio)ethyl-N"-methylguanidine disclosed in Spanish Pat. No. 455,991 (Chemical Abstracts, 89, 146904I (1978)) can be mentioned as the precursor that can be converted to Cimetidine by forming an imidazole ring at the final step. A diacetyl compound which is a starting compound for the synthesis of this precursor has a violent foul smell and aggravates the working environment, and the yield of the precursor is not sufficiently high.